Project Summary Diabetic retinopathy (DR) is one of the five most important causes of visual loss in the US population with 12,000-24,000 cases of DR-related blindness every year. Clinical phenotypes in DR include no/mild DR to sight threatening diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR). The severity of DR varies widely among patients and the biological underpinning for the phenotypic variability in DR is not completely understood. Some diabetics do not develop DR at all, or very mild DR in spite of long durations of diabetes. Not all diabetics develop DME or PDR. Our preliminary work presents novel evidence that the majority of PDR patients do not have concurrent DME, and similarly the majority of DME patients do not have concurrent PDR. Also, there is differential response to anti-VEGF drugs in DME and PDR. The variability in phenotype and anti-VEGF responsiveness in DME supports a genetic component in DR susceptibility. The goal of our research is to determine what factors are responsible for this phenotypic variability in DR, and discover a ?molecular profile? that quantitatively correlates with, and can thus be used to predict disease severity. In this research proposal, we utilize both hypothesis-driven and unbiased genomic approaches using next generation sequence technology (NGS) to investigate the molecular basis of phenotypic variability in DR. We hypothesize that either rare genomic factor(s) or the combination of environmental and rare genomic factor(s) that predispose to different DR phenotypes, or protect against the progression of DR. The specific aims include: 1) establish and segregate pure phenotypes of DR, DME and PDR in three ethnic populations; 2) identify and characterize the genetic factors and molecular pathways that influence the progression of DR and segregation of different subsets of DR by using whole exome sequencing; 3) determine differences in protein biomarkers that differentiate DR phenotypes using protein analysis. Use of next-generation sequencing (NGS) in this proposal will overcome many of the barriers associated with identifying genetic modifiers. We have assembled a unique team of experts in DR phenotyping and genomic studies to investigate genetic variants in DR. Our research will address a critical scientific gap in understanding phenotypic variability in DR and will define a ?molecular profile? that correlates with and predicts disease severity. Our findings may provide a tool for early prediction of disease severity, development of novel biomarkers, and improved therapeutic targets that may prevent the progression to severe vision threatening phenotypes in DR patients.